The National Crime Agency said it had uncovered hundreds of paedophilia suspects. Photograph: Dan Kitwood/Getty Images

Britain's senior police officers said they were at risk of being overwhelmed by an unprecedented number of child abuse investigations after the arrest of 660 suspected paedophiles.

The National Crime Agency (NCA) said it had uncovered hundreds of Britons previously unknown to police, including teachers and doctors, who had been using hidden corners of the internet to view obscene images of children.

Simon Bailey, the national police lead on child protection and abuse investigations, who is also chief constable of Norfolk, said: "Policing is facing an unprecedented increase in the number of reports in relation to historic and current child abuse. Chief constables around the country are having to arrange our resources to manage the threat and crime that is posed to some of the most vulnerable people in our communities and we are doing that on a daily basis."

The volume of investigations means that officers said it would not be possible to eliminate viewing of child abuse material simply by detaining the perpetrators.

Phil Gormley, the NCA deputy director general, said: "Are we going to be able to arrest our way out of this problem? I doubt it."

The six-month investigation, Operation Notarise, which was coordinated by the NCA and involved each of the UK's 45 police forces, led to 431 children who were known to the suspects being safeguarded, including 127 considered to be at serious risk of harm.

Detectives said that 39 of those arrested were on the sex offenders register, meaning the vast majority of the 660 suspects were never on the police's radar. Those arrested had used the internet, including the so-called "dark web", to swap child abuse material, but were tracked down using specially trained cybercrime experts who passed intelligence to forces across Britain.

Gormley, who led the investigation, said publicity surrounding the Jimmy Savile scandal and the convictions of Rolf Harris and Max Clifford had "broken a barrier" that previously prevented child abuse victims from coming forward.

Among the 660 suspects, the Guardian has learned that a junior doctor in the paediatrics department of a Lancashire hospital was charged with engaging in sexual activity with a child and possessing more than a million indecent images of children.

The doctor was among 19 suspects employed in positions of trust and sensitivity, including six teachers, four other school staff, two police workers and a scout leader.

Gormley said: "I'm pretty appalled about what it says about human nature. Which is why we need to think very carefully about what this means and how we approach this type of offending behaviour, and the propensity of quite large numbers of people to view this material."

The suspects include:

• A man who told police he had viewed child abuse images for three decades, since he was 16, and had regularly travelled to Vietnam, Cambodia and Thailand "for sexual purposes".

• A foster carer with no previous convictions who was caring for a vulnerable child when he was arrested. Four computers and one phone were seized by police and the suspect has since attempted serious self-harm, detectives said.

• A man who was part of an online group that shared films in which he abused a child, including footage which featured "the most serious form of abuse against very young children".

• A registered and violent sexual offender, who was already being prosecuted over the rape of a 13-year-old girl when police officers discovered a stash of child abuse images at his home.

• Another suspect arrested at an address where he had access to his 17 grandchildren, including two who had previously said they were abused by the man.

A total of 9,172 computers and mobile phones were seized by police during the investigation, with 833 premises searched across the UK.

Gormley said the NCA's ability to co-ordinate each of the UK's 45 police forces had led to the breakthrough in the investigation. "We've got an agency for the first time that has the responsibility of leading and coordinating the national threat and we've done it. Secondly, it's been identified as a threat we must respond to."